We propose to investigate the complex relationship between behavioral state and sensory processing in a high-order sensory-motor area. In the avian song system, nucleus HVC is a key forebrain nucleus that links auditory and vocal motor pathways. Consistent with a role in auditory processing, HVC neurons in sleeping or anesthetized songbirds respond robustly to the bird's own song (BOS). Surprisingly, in awake birds these same neurons respond quite variably and are no longer exclusively tuned to the BOS. Thus auditory responses at one recording site can vary over a few hours from complete suppression to robust. Because arousal selectively suppresses HVC auditory responses without affecting the auditory forebrain structure Field L, the avian analogue of the auditory cortex, we hypothesize that auditory responses in HVC, or auditory structures directly afferent to it, are modulated by changes in behavioral state. We will investigate the mechanism for these modulations in the adult zebra finch (Taeniopygia guttata). Our goal is to understand both the behavioral conditions that modulate auditory responses and the mechanism. In AIM 1, we propose to use our ability to suppress auditory responses in HVC by brief arousal of lightly sedated birds to identify the auditory structure afferent to HVC where arousal first suppresses auditory responses. Having identified this structure, we will then test the mechanism of arousal-mediated suppression of auditory activity by recording from HVC while pharmacologically manipulating neuromodulatory systems in the target structure identified above. In AIM 2, we use a song discrimination task to investigate whether auditory responses in HVC are modulated by attention. We hypothesize that attention will enhance auditory responses in HVC. In AIM 3, we propose to record HVC activity while the bird hears and interacts with conspecific males in his colony. We hypothesize that the behavioral context with which the heard song is produced as well as the identity of the singer will significantly influence auditory responses.